Electric incandescent lamps



Aug. 23, 1955 R. o. NYE ET AL 2,716,201

ELECTRIC INCANDESCENT LAMPS Filed May 14, 1953 1771/87? fol-6 Rovzczzcl 0. Nye

United States Patent Ofi ice 2,716,201 Patented Aug. 23, 1955 ELECTRIC INCANDESCENT LAlWIS Ronald Oliver Nye, Hillingdon, and Clilford Richard Sterling, Cockfosters, England, assignors to Hivac Limited, Harrow-on-the-Hill, England, a British company Application May 14, 1953, Serial No. 355,032

1 Claim. (Cl. 313-276) The present invention relates to electric incandescent lamps and is more particularly concerned with small lamps of generally tubular or cylindrical shape such as are widely used on telephone switchboards. Lamps of this type are ordinarily operated at a comparatively low voltage, for instance 50 volts, and are often provided with a carbon filament. Moreover if the lamps are used on telephone switchboards, it is often desired to mount a large number in a small space and they are usually mounted with their axes at right angles to the face of the switchboard, in other words the lamp provides the necessary light almost exclusively from its end. In order to secure sufiicient illumination in these circumstances it is usual to employ looped carbon filaments and this involves certain manufacturing difiiculties in ensuring that the filaments shall be mounted sufiiciently centrally to stand up to vibration and possible rough usage without touching the glass envelope. The present invention is concerned with an improved filament mounting arrangement for lamps of this type, whereby a more satisfactory product is obtained and the expectation of life of the lamp is increased.

According to the invention in a lamp of the type described in order to reduce the possibility of contact between the filament and the envelope, movement of the filament is restricted by a disc of mica or other suitable insulating material which is disposed substantially at right angles to the axis of the cylinder and through which the legs of the filament or the leading-in wires pass.

The invention will be better understood from the following description of two preferred embodiments which should be taken in conjunction with the accompanying drawings comprising Figs. 1 and 2.

Fig. 1 illustrates the invention applied to a tubular switchboard lamp of the type commonly used, while Fig. 2 shows a modification comprising a somewhat smaller lamp with a shorter filament.

Referring now to Fig. 1, the lamp envelope is indicated by 1 and this is sealed at the pip 2 after evacuation. 3 and 4 are the leading-in wires and these are sealed through the envelope 1 and extend to the glass bead 5 which unifies and steadies the whole construction. The leading-in wires are joined in the usual manner to the looped carbon filament 6 and this is supported during manufacture and against undue vibration subsequently by a mica disc 7 which is provided with suitable openings.

This disc is supported on a metal rod or post 8 which is secured to the bead 5. Conveniently the disc 7 is provided with holes through which the filament is threaded or alternatively the disc may be nicked with angular openings so that the filament may be inserted at the edge. In the form shown in Fig. 1, the disc 7 is slightly less in diameter than the internal diameter of the envelope 1 of the lamp and though a close fit is desirable it is not essential that the disc should touch the envelope since one of its main functions is to assist in centering the filaments while the sealing-in operation is taking place. The periphery of the disc may be provided with bent-over lugs or cars giving resilient contact with the envelope so that the disc would receive some or all of its support from the envelope.

In the modified form shown in Fig. 2 the filament is appreciably shorter and the advantages of the invention are obtained by passing the leading-in wires through the mica disc which can then be supported on the glass bead. In the arrangement shown in Fig. 2, the leading-in wires 11 and 12 pass through the envelope 10 to the glass head 13 and are connected to the filament 14 after passing through the disc 15 which is supported on the head 13. In order that this arrangement may be satisfactorily the leading-in wires are cranked as shown.

It will be appreciated that the use of a disc in this manner serves to some extent as a heat shield and tends to prevent the end of the lamp to which the connections are made from becoming overheated. The disc, moreover exerts some reflective efiect so as to direct the light in the direction in which it is required.

The invention therefore provides additional possibilities for the production of so-called indicator lamps of small size thereby tending to reduce the size of telephone switchboards where large numbers of lamps have to be mounted in close proximity.

We claim:

An electric incandescent lamp comprising a substantially cylindrical glass envelope closed at one end by a substantially hemispherical portion, leading-in wires sealed through said envelope at the end remote from the hemispherical end, a glass bead supported on and embracing said leading-in wires, a carbon filament supported by said leading-in wires and having a loop adjacent to said hemispherical end, a post extending substantially axially within said envelope and supported by said bead and an insulating disc of slightly less diameter than the internal diameter of said envelope supported at the extremity of said post substantially at right-angles to the axis of said envelope, said disc being provided with holes through which the legs of said filament pass whereby the movement of the filament is restricted and the possibility of contact between the filament and the envelope is reduced both during manufacture and during use.

References Cited in the file of this patent UNITED STATES PATENTS 648,516 Ochs May 1, 1900 692,294 Jaeger Feb. 4, 1902 1,034,722 Merritt Aug. 6, 1912 2,169,112 Scott et a1 Aug. 8, 1939 2,419,395 Foote Apr. 22, 1947 

